The present invention relates generally to a system for controlling the use of steam within a building and more particularly to a system that can control the flow of steam to minimize peak demand.
In large metropolitan areas, it is not uncommon for a central boiler system to be used to generate heat for multiple facilities in the surrounding area. This heating system is sometimes referred to as district heating or teleheating. The steam is transported via insulated pipes to subscribing buildings, which purchase the steam from the steam utility. Similar to an electric meter, a steam meter measures the amount of steam used by a particular building and the building owner is charged on a periodic basis.
In some areas it has grown expensive or impractical to add more capacity to the existing steam generation and distribution system. For example, real estate prices may make the properties in the area more valuable as an office building rather than a steam generation plant. As demand grows, the capability of the steam utility to provide necessary amount of steam may be strained. This capacity gap is most evident during the peak times of the year.
The steam distribution system is typically designed for peak demand periods. Unfortunately, the peak demand is only for several hours each year, typically on a cold weekday morning. Since many buildings are not used at night steam usage is low. In the morning, the building heating systems are started up resulting in an increase in demand for steam. Since most buildings start to increase temperatures at a similar time, the demand problem becomes compounded.
By designing to the peak demand periods, the steam generation and distribution system has excess capacity for large portions of the year. To encourage customers to conserve steam and reduce usage at peak times, steam utilities have implemented “net-metering” programs that charge customers different rates depending on not only how much steam they use, but also based on when the steam is used. Typically, a peak-demand charge is based on the highest demand from the customer during any thirty minute period during peak hours. Thus, customers who can reduce their usage during the early part of the work day pay less for their steam. If many of the steam utility customers adopt this manner of operation, then the steam utility can add additional customers without adding capacity. This way, more customers share the same expense, keeping the cost of steam stable in the long term.
While existing steam based building heating systems are suitable for their intended purposes, there still remains a need for improvements particularly regarding the reduction of peak demand in a manner that makes more efficient use of the existing steam distribution system while providing desired heating conditions for the customer.